I'm getting close to switching to a roller cam in the big block!

[HawkRod]

Your new springs will be 400# for a few days or running until they settle in to the upper 300s. Unless you really want to upgrade, I suggest you save your money. If you had a race car doing 7000 RPM and your springs were in the 500# range and up I'd worry about it, but for a street car I think you'll be fine.

 

[BSB67]

View attachment 1926914

By looking at the two cams in the attachment, you cannot say which is more aggressive.

Aggressive speaks to the rate that the lifter and valve moves. The contact point between a roller lifter and a roller cam lobe is completely different than the contact point between a FT lifter and FT cam lobe. The contact point effects how the lifter accelerates.

Said differently, if you put a roller lifter on a FT cam lobe, it would move the lifter and valve way slower than a FT lifter on the same lobe. The valve and motor would see it as a smaller cam, and it would make a bunch less power.

 

[Geoff 2]

The contact point does NOT affect how the lifter accelerates. It is merely the contact point. The lifter does not know what is to come after the initial contact has been made.

 

[BSB67]

The contact point does NOT affect how the lifter accelerates. It is merely the contact point. The lifter does not know what is to come after the initial contact has been made.

Okay. It is the contact point between the lobe and the lifter relative to the centerline of the lifter.

 

[BSB67]

Here is a diagram that shows why a roller cam lobe profile “looks” more aggressive than a FT lobe profile to get the same lift rate as the FT.

The diagram would be an example of what happens with a roller lifter relative to a FT lifter on the same cam lobe. To get the same rate of lift for a roller lifter, the cam lobe needs a more aggressive shape.

 

[icetech]

Here is a diagram that shows why a roller cam lobe profile “looks” more aggressive than a FT lobe profile to get the same lift rate as the FT.

The diagram would be an example of what happens with a roller lifter relative to a FT lifter on the same cam lobe. To get the same rate of lift for a roller lifter, the cam lobe needs a more aggressive shape.

View attachment 1933573

thanks for that drawing , i had never considered how much farther into the lifter the contact point is on a roller.. had never really thought bout it though